司馬昭之心路人皆知

sīmǎzhāozhīxīnlùrénjiēzhī ㄙ ㄇㄚˇ ㄓㄠ ㄓ ㄒㄧㄣ ㄌㄨˋ ㄖㄣˊ ㄐㄧㄝ ㄓ

    • lit. Sima Zhao's intentions are obvious to everyone (idiom)
    • fig. an open secret

Character by character

Saying俗语俗語

Two-part saying歇后语歇後語 · In everyday use

Literally
Sima Zhao's intentions: even passers-by know them
Meaning
Someone's scheming is so obvious that everyone sees it. Mocking or critical; the first half alone is commonly used.

Sources